1. Field of the Invention
The present invention relates to an exhaust manifold for an internal combustion engine, and more particularly to an exhaust manifold the inner surface of which is lined with a heat insulating material.
2. Description of the prior art
Hitherto, various kinds of exhaust manifolds have been proposed and put into practical use in the field of internal combustion engines. In order to reduce the weight, some of the exhaust manifolds are constructed of light metal, such as, aluminium or the like. When using aluminium as a material of the exhaust manifold, it becomes necessary to line the inner surface of the manifold with a heat insulating material because of the poor heat resistance of this metal.
Some of the hitherto proposed exhaust manifolds have employed a ceramic fiber layer as the liner. However, due to its inherent construction of the liner, prolonged use of this type of manifold tends to induce undesirable peel-off phenomenon of the inner surface of the ceramic fiber layer which is exposed to the highly heated exhaust gas emitted from the engine. Of course, this phenomenon induces thermal damage (such as melting or the like) of the aluminium body of the exhaust manifold. This undesirable phenomenon is particularly notable at the inlet ports of the manifold which are directly attached to the highly heated exhaust ports of the engine.